Best Big Bore Kit for 400EX

[DaveEX7]

which bore kit would u go with for ur 400 if u have already??

[Ben]

For my money, mostly trail and very little track work, I would go with a good quality 426. Something that gives you good performance gains but still retains the stock powerplant's excellent reliability :) From talking with Scott at Pro Fab ATV he says that a nicely built 416 will give you similar results but that the 426 is priced almost equal to the 416 and does certainly give a bit more power than the 416. The bigger bore kits, imho, sacrifice too much reliability.

Ben

[DaveEX7]

thanks ben, how much is the 426 run from??

id personally go with a 500 stroker if i had hte money

[Ben]

Their 426, which sounds very nice, I believe runs around $700+, but he told me over the phone that he can do it cheaper if you don't add all the components to it For that price he builds it for you, just ship the engine to him. Check out ProFabATV.com for his prices and building specs. Anything over a 426, and especially over a 440, in my opinion and many others opinions, is way too radical unless you are a "nationals" race rider and can afford to rebuild it quite often.

Ben

[DaveEX7]

my first choices were either a 440, or a 500 stroker... but it makes sense cause i dont race, except in our own lil custom tracks with the biggest jump bein a 20 foot step-down, so i really dont need all that extra power so now its either gona be a 426 or 440

[DaveEX7]

i juss got done lookin through white brothers magazine, and theres a 440 kit in there for $306.00.... isnt that kinda cheap for a kit of that size

[Dave400ex]

Yep stay with a 416 or 425/426. The only way I would do a 440 is bore to a 416, then stroke it to a 440, which would be more reliable.

[DaveEX7]

i dont think id wanna go through all that trouble.... well the first thing im gonna get is the system cause the kit aint gonna do crap if i dont have somethin to back it up, and then il have to save all over again cause i still have to save for the 400 to get it

[Dave400ex]

Well really after reading the Posts from Maryland 400ex, I would get a Full Pipe, then the 39MM FCR before I got a Piston and Cam.

[RIDER11X]

Originally posted by Ben
Their 426, which sounds very nice, I believe runs around $700+, but he told me over the phone that he can do it cheaper if you don't add all the components to it For that price he builds it for you, just ship the engine to him. Check out ProFabATV.com for his prices and building specs. Anything over a 426, and especially over a 440, in my opinion and many others opinions, is way too radical unless you are a "nationals" race rider and can afford to rebuild it quite often.

Ben
is more reiability retained by stroking to the desired cc, and staying with the stock bore size? would this even work?:confused:

[Dave400ex]

If you are going to Bore/Stroke it, I think the best setup would be to Bore it to a 416, which isn't a huge overbore and won't hurt your engine much at all, and then Stroke it to a 440. That would be powerful, and have some serious Torque.

[DaveEX7]

il try that..... as u said it should be very powerful

[jaime_honda]

Hey, I have a IMS 440 Kit, and just love it. My friend has the 426 Kit and when we race I always blow right by him. Go with the 440 you will end up falling in love with it.

Below is a picture of my ride!!:blah

[Predator36]

Reliability of any 400ex engine that has a larger sleeve installed is totaly dependant on the engine builder and the guy that installes the sleeve. If the sleeve is not installed properly - you will blow head gaskets, if the wrong head hasket is installed you will blow head gaskets, if the compression is to high for the application and fuel octane - you will pull the head studs loose. If all is done correctly it will last a long time.

[440exnacsracer]

predator...your right. since last june when i got it bored out by a d/a, i bought over 10 head gaskets, got heli-coils for my studs cause they were stripped, bought a new sleeve and piston cause they seized up and i think thats about it,,...minus the 60 days ive missed ridin. i get her back on tues. though...hopefully itll run like a champ.